1. Field of the Invention
The present invention relates to overhead exposure units for reproducing film images on photosensitive sheets such as silk screen, films, printing plates and the like used in the graphic arts industry. In particular, the present invention is directed towards a new and improved light exposure unit in which a light source is positioned with a relatively short distance between the light source and a silk screen, film or sheet on which an image is being reproduced so that a relatively high light intensity is afforded thereby minimizing the exposure time interval required during an operating exposure cycle. All this is accomplished in a unique overhead exposure unit wherein a light source, a glass panel and a supporting panel frame are pivotally movable relative to a horizontal base and vacuum blanket between a first or exposure position and a second or open position for providing easy loading and unloading of the film, silk screen, sheets etc.
2. Background of the Prior Art
In the past, many overhead light exposure units have employed high intensity lamps enclosed within a lamp housing supported and maintained at a fixed level or distance above a horizontally disposed vacuum frame assembly used for holding films and sheets, etc. in registration for reproduction and platemaking operations. With the advent of ever larger size vacuum frame assemblies, it has been necessary to increase the exposure spacing or distance between the light source and the vacuum frame assembly in order to provide a large enough space between an upwardly tilted, glass supporting frame and the horizontally disposed vacuum blanket. The open space is needed for both convenient viewing and registration of the materials and for easy loading and unloading of the film and sheet materials into and out of the exposure apparatus. This increase in the light source to frame exposure distance has been objectionable because unacceptably long exposure times have been required and production rates have thus suffered.